Mailinglist Archive: opensuse (818 mails)

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Re: [opensuse] Recover Linux Raid 0 with 2x2port 3Ware Raid 1 cards
On 08/31/2011 05:45 PM, LLLActive@xxxxxxx wrote:
Hi all,

I have an openSUSE 11.4 32Bit system installed on its own disk. Additionally
attached are 2 mirrored 2-Port 3Ware raid cards, striped as Linux Raid, then
mounted as /home/Data (ext4).

The softraid was mounted after the OS installation within fstab, because I
wanted Data to be on the raid and not be dependent on or be part of the OS FS
directly.

I've never had a softraid before. Hard-Raid recover is painless with 2Ware, and
immune to failing OS. I got a backup of the 4 TB raid; it has 2 TB data and a
restore takes quite a while.

Now I lost my OS Installation, the disk is unresponsive. Before I go ahead, I
was wondering which way to go.

I am planning to install a new system and just hope the soft raid will be there
when I partition. What should I watch out for? I have searched and read some
ways to recover defective raids in the TLDP.org and others, but the raid was ok.
It was a mount as /home/Data directory. I will mount it after the new
installation as /home/Data again. Will that work ok? How does the raid-setup
work? Is the raid-partition info kept on the disks? There is no controller with
bios as in hardware raid to store the Linux softraid info. As far as I know,
HW-raids save the raid-partition info on the disks and on the controller. How is
it in softraid?

:-)
Al


Oh no!

Seriously, I think you will be fine. Both dmraid (fake raid) and mdraid (software raid) are mature and robust enough to easily rebuild/recover for a mirrored raid failure if there is a complete crater of one of the disks in the array. If I understand your post well enough -- you don't even have that problem. If I have this straight you have:

----------------
Computer
OS Disk (failed)
3Ware - 2 port striped (OK) ]______ mirrored mounted as /home/Data
3Ware - 2 port striped (OK) ]
----------------

If the OS disk is what is dead, you should be able to reload the OS on a new disk without even connecting the 3Ware controllers. After you are happy with the new install, then just reconnect/plug in the 3Ware controllers and re-create the mirrored array using the same config as you had originally. I have never had much of a problem getting a new install to recognize and use and existing software raid array. You can even move them machine to machine without a problem. Fakeraid (dmraid) is a bit more of a problem to move from box to box due to the BIOS dependent array setup and rebuild.

Others may need to fill in the fine point, because I haven't ever done the recreation of a mirrored set of striped arrays before on a new install. However, from the standpoint of just reloading the OS and then recreating the mirror of the 3Ware controllers and mounting as /home/Data -- it doesn't seem that bad.

Good luck!

--
David C. Rankin, J.D.,P.E.
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